The answer to “how long” is of course “longer”. But like I say the amount of time we have to play in is huge, orders of magnitude longer than all of human history to date.
I find it implausible to imagine a flame-retardant world where our plucky species doesn’t manage to harness fire even with hundreds of millions of years of sentient-species-ish exploration and tinkering. No burning swamp gas, no high-friction phenomena, nothing that burns when exposed to lava, and on and on.
Bear in mind that powered flight is barely a century old.
The 10s of millions of years I was allowing humans to do this project, obviously includes the negligable thousands of years it will likely take for humans to make such improvements to our probes. I was saying conventional propulsion to make it clear that we aren’t assuming FTL or anything. But yes we can and obviously will improve our probes beyond Voyager.
They do not have a generalized abstract problem solving ability however, so I don’t see how your response addresses my point at all.
Lumpy, spagnum peat is a fossil fuel and has been used as such for thousands of years. Bog fires are also a thing.
You seem to be creating a defining the term “generalized abstract problem solving ability” in some way to tautologically exclude any species but humans. Canines (wolves, domestic dogs), ursines (bears), and primates (chimpanzees, gorillas, orangutans) have all demonstrated some degree of being able to interpret and solve challenging problems beyond anything that could credibly be termed as instinct, and in fact the psychology of animals is largely dependent upon observing their approach to novel situations. If you’ve ever worked with and trained herding dogs you can see them learn from experience and anticipate outcomes. We struggle to understand the signals that they relay and interpret to each other, even though their cognitive abilities are certainly more limited than our own with a correspondingly less complex vocabulary. We essentially have no idea what cetaceans are saying to one another, and they are most certainly capable of abstract problem solving. The notion that an even more complex and completely alien species based on an unrelated biology would be easier to understand than other mammals in our evolutionary tree is risible and without logic.
Stranger
Will they? That’s my question. How well do cow hooves and crab shells burn? Afaik not particularly well, and carbonate mollusk shells, forget it. Cotton burns but wool and hair scorches and smokes, because the chitin and keratin from animals are proteins, whereas virtually all (earth) plant fibers are based on some variety of cellulose, a carbohydrate polymer that’s directly flammable. My original question is, out of all possible substances to build a stiffening structure, is it necessarily a slam-dunk that alien plants will build themselves out of cellulose? It seems to me that that’s not a given.
It’s important to our biosphere, because cellulose-based plant life made it possible. Again, we take this so much for granted that maybe we’re not even considering that it’s not universal.
Extremely improbable; radioactive elements are by definition fading away. Two billion years ago there were natural water reactors on Earth because uranium-235, with a half-life of about 100 million years, was in much higher concentrations then- not anymore.
They may not be wood as such but they are ultimately cellulose.
So your question isn’t that of wood specifically but of cellulose then? Understand that cellulose, or rather the lignocellulose structures that make up wood and other dense woody plant fibers, are carbon-based polymers that are, like virtually all chemical fuels, carriers for the hydrogen, the release of which ultimately produces the majority of exothermic reactions. There are, of course, other flammable substances on our planet, most of which are hydrocarbon-based because all life on Earth is based on hydrocarbons and the source of all of our non-geothermal energy is essentially solar radiation captured by photosynthesis. Cellulose is neither a necessary nor sufficient requirement for advanced civilization or industrial technology.
The question of the commonality of natural occurrence of cellulose or a similar polymer is valid, and given the relatively simple construction it seems probably that other carbon based life would produce it for structural and energy-storage purposes. But in the more general sense, there is no assurance that life will be formed in an atmosphere that will support open flames, and in fact there are good reasons to believe that carbon-based life may be more prone to form in environments in which combustion is not typical, e.g. liquid environments rich in reducing hydrocarbon compounds. In such a case, a different evolutionary path would have to occur in order to get to advanced technology, but that is neither improbably nor difficult to imagine.
[SUP]235[/SUP]U is relatively rare in Earth’s crust, but likely quite common within the lower mantle, where radioactive decay of uranium, potassium, thorium, and potentially transuranic elements which are bred in a natural fast reactor environment drive the seismic processes of the Earth with energy which dwarfs all fossil fuel reserves. A planet that is more volcanically active, or which began with much richer sources of actinoids due to being in an area of the galaxy in which supernovas which produce those elements are more common, may have much larger amounts of fissile and fissionable materials. Such an environment would be quickly lethal to our form of life, but the intense energy gradients may be ideal for a more hardy construction and robust against ionizing radiation, and the high level of available energy might drive reproductive and evolutionary cycles faster than our relatively simple CHNOPS chemistry using ATP for energy transport.
Making statements about the probability or lack thereof of extraterrestrial life has to be caveated by acknowledging that we have zero empirical evidence to base even speculation, and we can only imagine the kind of exotic chemistry or even non-chemical forms of self-organizing, self-reproducing systems which could develop something akin to cognition (although I suspect life, if common, will be based on carbon-nitrogen-hydrogen chemistry just because those elements are so terribly common throughout the universe and allow for very sophisticated structures). Being dismissive about the potential for life in a form very different from our experience is due to a lack of imagination or knowledge about what alternatives may be workable within chemistry and evolved in environments very different from our own. Even we, and most life on Earth today, could not survive in the conditions of primordial Earth, nor could life that existed then last long in our oxygen-rich atmosphere.
Stranger
We actually have 2 significant pieces of evidence :
a. Self replicating machinery is possible, as we already have it* and are composed of it.
b. The universe appears quiet - there does not seem to be an infestation of self replicating machinery we can see from here.
This means that either something is likely to happen to us before we develop self replicating machinery that is robust enough to expand across the universe forever, or life at the stage we are at now is exceedingly rare. Or c, some pessimists about technology might deny that self replicating machinery capable of interstellar expansion is possible or discoverable by humans (even if it takes another million years from now), but I discount that view as empirical evidence does not support it. You absolutely can draw up a napkin sketch of a working self replicating starship that depends on no physical principles we don’t already know.
Other possibilities, like ‘advanced alien races choose not to expand’ are simply based on ignorance of evolutionary pressures.
Note, first of all, I said “if in IMHO” in relation to the “number” I provided (which said forum we are not in), which I guess you completely missed in your urge to insult me. Likewise I am well aware of what the Drake Equation was intended for, but it most certainly DOES well reflect the general very long odds, even if only in a rudimentary way. [He has-what-8 or 9 terms? There may in fact be hundreds.]
Fine, if you want your “evidence” (while providing none at all for your “nothing special” supposition)-I simply assumed that you were knowedgeable enough to take these as givens:
[ul]
[li]Life coming together in the first place[/li][li]Evolution of DNA or other replicating molecule[/li][li]Having a planet whose star has been stable for 5 billion years (or no dangerous companion stars) to allow life a chance to evolve[/li][li]In a solar system which has otherwise been stable (since the alleged impact of Theia which formed the moon)[/li][li]The existence of the moon, which might moderate changes in our axial tilt, thus keeping our seasons from going completely out of whack[/li][li]On a planet which has been remarkably stable climate wise, relatively speaking (and volcano etc. wise)[/li][li]The mitochondria importation event, allowing for eukaryotic cells to use a lot more energy than prokaryotes, thus allowing for large multcellular life[/li][li]No truly life, or even planet, threatening impact events since Thera[/li][li]No other such events of other sorts[/li][li]Evolution of life on land (may be inevitable, may not be)[/li][li]Evolution of opposable thumbs or such allowing for tool use (I have posited that elephants might have (had) a chance since their trunks could evolve in similar ways)[/li][li]Evolution of high intelligence[/li][/ul]
Are you truly ignorant of all of that? I probably missed a lot, or at least some things which are a subset of what I listed. To have all of that happen to this planet is truly mind-boggling, to be honest. We have won the cosmic lottery, several times over. To have to point that out to anyone here, in this thread, is like having to point out the existence of Babe Ruth to someone in a baseball thread arguing that someone else is clearly the best player of all time (which they may be, but you MUST acknowledge the Babe if you do). Earth is thus almost certainly the least mediocre planet for a good long distance around.
Note I am NOT thus positing any sort of true miracle here, but these hurdles/filters are essentially the kinds of things that ANY intelligent species must overcome to even have a ghost of a chance to exist in the first place. Life in general has probably popped up many times, I’d wager, but most of it probably get nuked by something before it even has a chance to become multicellular and then intelligent.
[This is usually why I don’t post in this subforum, because of all of the black/white thinking that often is found here, where everybody is just hankering to glom onto a nitpicky “gotcha” that someone else may have committed. Yawn.]
Thanks, I really enjoyed that.
There was no intent to “insult” you, but only to show that you were making strong definitive statements based on nothing but belief and no actual evidence whatsoever. The list of “evidence” you now provide for the supposed miracle of life on earth is just a list of common platitudes in two broad categories, astrophysical events and evolutionary events. Since there is no reason nor evidence to suppose that such events are particularly rare among the roughly 300 billion stars in this galaxy alone, these arguments are completely banal. A star’s stable lifecycle is largely predictable from its mass, for instance – it isn’t luck; there is nothing in the solar system or this part of the galaxy that can be identified as astronomically unique; chemistry is the same everywhere, and the elemental makeup of second-generation protoplanetary systems will have only statistical variability.
Indeed from what we’ve now observed of the abundance of exoplanets, many in the habitable zone, the default assumption that we are NOT, in fact, a 1-in-300 billion odds miracle in this galaxy for some inexplicable reason winning the “cosmic lottery” over and over again, but are merely an incidence of a commonplace event, rises from the level of a logically compelling argument to one that is increasingly supported by actual evidence. The real miracle is the homogeneity of the universe and the beautiful consistency of its fine-tuned physical laws, that very lack of “specialness” within its vast scale of space and time. To believe, instead, that what happened in this little planetary system off in an obscure corner of the Milky Way is an almost impossibly unlikely freak of nature seems to verge on the absurd.
You’re partly right. The actual list of events doesn’t tell you about the probability of those events. Like I argue above, though :
If you’re right, and the sequence of events that led to you and I being able to communicate in this manner was a common possibility, why do you not see the evidence right now?
What should happen is that very soon ish (might take 1000 years, doesn’t matter), we will develop a small factory that can copy itself and a more durable version (and probably more advanced version) of our own minds. There is no credible evidence to say this won’t work, and in fact, the only reason this wouldn’t work would require divine magic or some other nonphysical explanation for human intelligence. (which in turn also breaks your logic chain above, because it would mean that human intelligence can’t evolve naturally)
Once we have created such devices, they will be under evolutionary pressure to use all available matter. The end state would be a starship traveling to every star in our galaxy through the most rapid feasible means (known to us now, that would be antimatter fuel and a substantial fraction of the speed of light) and development of enough living robotic matter around every star to consume all available rocks around that star.
The evidence of this should be visible through telescopes. Every star should have a different spectrum, radiating more infrared, and there should be no exoplanets left. (well, not small ones - even with exponentially replicating factories, harvesting a gas giant might be tough)
Note I don’t believe in the kardashev scale, I don’t think using all of the energy of the star would be necessary. Just using all of the available solid matter.
Obviously not, because it’s also including our hypothetical ET species.
I’m describing part of the difference between sentient and non-sentient life.
FTR I think it’s a stretch to call them challenging problems not based on instinct, but I’ll put that to one side as these are somewhat relative terms and we’ll obviously never agree there.
The point is this: The idea that We can’t communicate with animals, so how could we possibly communicate with ETs? is based on a questionable premise and a bad extrapolation.
The premise is questionable because we frequently communicate with animals. What makes us think they have more to tell us than we are currently aware? Disney movies?
The bad extrapolation is making a statement about an advanced form of sentient life based on a non-sentient species.
One thing we can know, is that an interstellar ET has solved problems far more complex than decoding a structured language.
It’s not enough to say Maybe they communicate through smell? or whatever.
To make interstellar spaceships they would have had to study, and solve, and form a deep understanding, of countless phenomena that have nothing to do with smell.
And those phenomena in many cases leave few clues around.
By contrast human spoken and written language is available as yottabytes of data littering our world in all kinds of media, and with clear structure and patterns. A piece of piss compared to the problems they’re used to.
I’m always fascinated by the euglena – which, despite engaging in photosynthesis, lacks a cell wall, because life sometime comes in downright bizarre forms.
Fire isn’t enough on its own, but if you can’t do fire, what can you do? You can have an intelligent aquatic civilisation, but not a spacefaring aquatic civilisation. They can’t do fire, they can’t do metal-working or glass or pretty much any technology. If oyu can’t make a knife you can’t just jump straight to rockets or manipulating lava.
Fire isn’t enough on its own, but if you can’t do fire, what can you do? You can have an intelligent aquatic civilisation, but not a spacefaring aquatic civilisation. They can’t do fire, they can’t do metal-working or glass or pretty much any technology. If oyu can’t make a knife you can’t just jump straight to rockets or manipulating lava.
Fire isn’t enough on its own, but if you can’t do fire, what can you do? You can have an intelligent aquatic civilisation, but not a spacefaring aquatic civilisation. They can’t do fire, they can’t do metal-working or glass or pretty much any technology. If oyu can’t make a knife you can’t just jump straight to rockets or manipulating lava.
As I said, there are sun-like stars a billion years older than our sun—so it seems plausible that the right environment for intelligent life as we know it has been around for at least a billion years; and all we need is one species with a 50-million year headstart on us in order to have the whole galaxy colonized.
Oh no, quite to the contrary. The scenario I described needs, at best, a passing, occasional interest to build a starship, coming up every couple of hundred thousand years, using up an utterly insignificant fraction of the economic resources available to the denizens of a given star system.
After all, I’ve given each star system a million years to send out two ships (which also should arrive within that timeframe—but what the hell, let’s call it two million years, it’s not gonna change anything)—that’s it. Look at what we’ve done in the last couple of hundred years, and then just think about the output of an industrial civilization across a million years—building a starship, even if we’re stipulating that it takes them a century and consumes the mass of a couple of asteroids, simply isn’t going to amount to any measurable fraction of the time and resources available.
So they don’t need any particular obsessive drive; in fact, they need far less motivation than humans have shown so far to leave their own star system. They can spend hundreds of thousands of years contemplating the precise topography of their navel(-analogues), and a barely non-zero interest in interstellar space travel will be sufficient to fulfill the loose parameters of my model.
Of course, the sort of exponential scenario I envisioned can be questioned on different grounds—one simply being that you’re going to run out of planets: the number of planets that can be visited in a certain amount of time is going to only grow cubically, so eventually, the exponential trend must halt (as all exponentials do in a finite world). But that’s why I’ve linked to the article using a much more realistic model, coming to basically the same conclusion based on likewise very conservative assumptions.
An aggressively spreading culture would achieve galactic saturation much quicker; but it suffices to assume a fairly leasurely exploration in order to bump into the Fermi problem.
I agree that it’s plausible that there are older and therefore likely more advanced civilizations than ours, but I was referencing the earlier cited paper that hypothesizes that we may be one of the first, which is one possible answer to the paradox. But personally I subscribe to the idea that in terms of the extremes of the chronology of intelligent life, we’re most likely in the most populous part of the bell curve.
Point taken, and I should retract that part about “… to do nothing but propagate itself from star to star …”, but IME some strong points remain about the necessary long-term motivation for them to do this – even if this exploration urge is intermittent, we still have to make a whole lot of assumptions including the fact that they will keep wanting to build starships and move on to the next stellar system even after a hundred thousand years and unimaginable technological and cultural evolution. Why would they? And furthermore, your hypothesis seems to assume that the next founded civilization on the next stellar system would want to do the same thing. Would they? And would there even be a next one? It might take a few thousand years to get to the next nearest star system, but what if there’s nothing habitable there? Maybe this particular ship – and many others just like it – may be out there for millions of years looking in vain for a place to colonize, until everyone on it eventually perishes.
IOW, your exponential growth assumes a consistently systematic pattern of expansion, which may be extremely unrealistic even if you allow many millions of years for it to happen. Exponential growth is indeed extremely powerful, but all it takes is a few systematic disruptions for it to stop dead, or never even get started. Kind of like how the decay of fissile material sometimes leads to really spectacular energy release, and sometimes nothing much at all.
I took a peek at the Wikipedia article on the Fermi paradox, and while the arguments against it are of varied degrees of plausibility, there are several that deal with cost and motivation; for instance:
It is too expensive to spread physically throughout the galaxy
It is possible, however, that present scientific knowledge cannot properly gauge the feasibility and costs of such interstellar colonization. Theoretical barriers may not yet be understood, and the cost of materials and energy for such ventures may be so high as to make it unlikely that any civilization could afford to attempt it … [or, I might add, that they would necessarily be motivated to send their fellow beings on multi-thousand year missions that are essentially one-way, to adjacent star systems that would, statistically, probably not even be habitable for them.]
They tend to isolate themselves
It has been suggested that some advanced beings may divest themselves of physical form, create massive artificial virtual environments, transfer themselves into these environments through mind uploading, and exist totally within virtual worlds, ignoring the external physical universe … Once any sufficiently advanced civilization becomes able to master its environment, and most of its physical needs are met through technology, various “social and entertainment technologies”, including virtual reality, are postulated to become the primary drivers and motivations of that civilization.
First of all, your assumption that non-human animals have no sentience is not shared by animal psychologists cognitive scientists. It is widely recognized and well established that all mammals, most aves, and many other distantly related species such as octopuses have degrees of sentience, and communicate with one another in often surprisingly sophisticated ways. Our communication with animals is very imprecise and imperfect even when dealing with domesticated animals that are evolutionarily adapted to respond to human speech and other modes of communication. We train dogs to respond to commands and cues, but have difficulty understanding many of their social behaviors by which the interact with one another, in part because many of those cues do not involve speech and facial expression which our brains are evolved to rely upon for communication.
The notion that communicating with an extraterrestrial species which shares no evolutionary history, cognitive structure, or possibly even basic chemical structure would be an “easy problem” is so absurdly dismissive and, in your terms, “a bad extrapolation”, it would seem that you are projecting some unfounded personal belief rather than any hypothesis grounded in reason or plausible analogue, such as communication with dolphins or whales which are far closer to us in cognitive structure than we could expect any extraterrestrial life to be.
Returning to the notion of a “Great Filter” as being any particular element in our evolutionary development such as fire, mechanical tool building or using, et cetera, we need to recognize that such constraints a result of a very narrow view of how intelligent life could develop some kind if industrial and technological capability. Just as we used to believe that the Earth and then the Sun were at the center of the universe, we have a tendency to think that our development and form is somehow special and privileged to represent a uniquely favorable evolutionary development instead of just the cumulation of various steps which represented solutions to the particular evolutionary pressures of the time. Why do we have trichromic vision, or a retinal nerve that goes backward through the eye creating a blind spot? Because that was the path human evolution followed, and there was not enough of a cost or pressure to get a different solution, even though the octopus eye, which fulfills the same essential purpose.
The Fermi paradox and this Great Filter hypothesis also assumes that an intelligent species would ultimately achieve interstellar civilization and grow to fill all available space and use all resources it could access. This is certainly what bacteria do, and to a certain extent even we do so, but an advanced species may have other agenda beyond physical expansion. It may not have a drive to explore and colonize the galaxy, or it may find that the costs of doing so are better spent in other ways of exploring the world, such as understanding the basic mechanics of the universe. The notion that all intelligent life would seek to exploit resources, build giant structures, and send messages everywhere seems to be as much grounded in the conquistador tradition of European colonization as any kind of basic philosophy. An extraterrestrial species would be so alien in its cognition and drives that there is no guarantee that their motives would be in any why comprehensible to us.
Stranger
Absolutely – thanks, Stranger, this pretty much reflects what I’ve been trying to get at with my refrain about “motivations”, but better said. The exponential colonization theory assumes that such intelligent life would not only have the same drives and motivations that we have at this present time in our sociopolitical evolution, but would sustain it across millions of years and across distributed disconnected multi-stellar colonies that were all evolving independently. I think that HMHW raises a good and thoughtful point about the power of exponential growth, but there are many reasons to believe it either may never have the necessary impetus to get started in the first place or else there may be disruptive factors that quickly end it. I just think there are too many assumptions behind it to believe that it’s so inevitable that we must be forced to look for explanations for why it hasn’t happened, since explanations for why intelligent life forms would not do this are abundant.
As for sentience among non-human animals on this planet, totally agree with that, too. One can even put aside all the scientific evidence and simply state the simple fact that anyone who believes that many advances species aren’t sentient must be someone who either has never owned a dog or has been spectacularly oblivious to it. Admittedly there is a wide range of canine intelligence, as their is among humans, but my dog has been capable of learning about human motivations, understanding them, and remembering the lessons for long periods; he’s been adept at problem-solving, and so adept at creatively expressing his wants and needs that you could practically hear the spoken words – lacking the power of speech seemed more like a physical disability than an intellectual one. If dogs aren’t sentient then neither am I.